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Computing Critical Path Drag in Start-to-start (SS) Relationships

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Stephen Devaux
User offline. Last seen 37 weeks 6 days ago. Offline
Joined: 23 Mar 2005
Posts: 655

There is a Wikipedia page that explains how to compute critical path drag, but only with finish-to-start relationships. I recently had a long discussion with another PP member, Dennis Hanks, in which I mentioned the value/importance of computing critical path drag and drag cost. Dennis looked at the page and indicated that the concept seemed not that valuable as drag "is confined to networks with only FS relationships!"

Now, since such an experienced and knowledgeable PM person as Mike Testro argues that networks should only use FS relationships, this might not be that big a problem. But for the record, it is not true that drag is only for FS networks. Drag is the amount of time something on the critical path (activity, constraint, delay, sprint) is adding to the project duration and, as such, can be computed in any planned schedule with any logic relationships. It does get a bit difficult to compute "manually" with large networks and with complex dependencies and lags. But it's not THAT difficult!

But this made me decide to edit the Wikipedia page to show a new diagram with SS + float relationships and shown an easy way to compute drag in such situations. If anyone has questions or wants to discuss, I will be delighted. The page is here:

(Of course, it's dead easy for a software algorithm to compute drag -- too bad so few of them currently do! But that will change in due course.)

Fraternally in project management,

Steve the Bajan